Hoist drive and brake mechanism



June 26, 1951 H. c. FITZSIMMONS 2,557,958

. noxs'r DRIVE AND BRAKE MECHANISM Filed April 5, 1948 2 Sheets-Sheet 1F fg.

INVENTOR. Harold C. Fitzsimmons BY a ays June 26, 1951' H. c.FITZSIMMONS 2,557,958

' HOIST DRIVE AND BRAKE MECHANISM Filed April 5, 1948 2 Sheets-Sheet 2F/gZ INVENTOR. C. Fifzsimrhons Attorneys Patented June 26, 1951 HOISTDRIVE AND BRAKE MECHANISM Harold C. Fitzsimmons, West Chester, Pa,assignor to The Sharplcs Corporation, a corporation of DelawareApplication April 5, 1948, Serial No. 18,983

1 Claim.

This invention relates to improvements in gear driving mechanisms andmore particularly to an improved form of a reversible gear drivingmechanism having automatically operable braking means to prevent reversedriving of the mechanism.

Hand-cranked crane hoist mechanisms are frequently used to lift the bowland related parts of the larger types of centrifugal separatingmachines. Such crane mechanisms are usually attached to the frame of thecentrifugal machine as an integral part in a manner to permit themovement of the crane boom over the machine so that the lifting cableand hook may be lowered to engage and lift the bowl or other heavy partsof the machine.

It has been common in such cranes to wind the lifting cable onto a drum,to mount on the drum a worm wheel and to engage this worm wheel with aworm rotated by a hand-crank. Worms and worm wheels were so chosen as toprovide a so-called self-locking or non-reversible system so that thegears could be readily turned by the hand-crank, but loads on the cranewould not cause rotation.

Such gear systems had a high ratio and provided for only slow raisingand lowering of the load. When attempts were made to increase the speedby lowering the gear ratio, the gear system became reversible ornon-self-locking, so that loads on the cable lowered spontaneously withaccelerating speed with damage to the load unless the crank handle washeld at all times by the crane operator. If the operating handle of sucha system should be lost from the grasp of the operator, it is obviousthat the operator would be risking his limbs in trying to stop therotating crank handle.

With such cranes having high lifting speeds and reversible gearmechanisms, various types of ratchet mechanisms requiring manualoperation by the crane operator were used. The principal difficulty withall of these were that the crane operator had to exercise considerabledexterity in manipulating the ratchet along with the operation of thehand-crank while lowering heavy loads, as it was necessary to hold theratchet out while lowering and to reset it before letting go of thecrank handle.

Such low ratio worm gear systems could be made non-reversible only bythe use of excessively large diameter worms with low angles of thethreads.

It is a principal object of this invention to provide an improved geardrive mechanism of the reversible drive type having automaticallyoperable braking means to prevent the reverse driving of the mechanismwhile not interfering with any desired rotation.

It is another object of this invention to provide a reversible drivegear hoist mechanism suit- I able for use in connecting the operatinghandle of a hand-cranked crane mechanism to the crane lifting cable drumin a manner to afford a high lifting rate of speed and havingautomatically operable means to brake the rotation of the lifting cabledrum in the direction to cause lowering of the cable without interferingwith the desirable high rate of rotational speedfor the cable drum inthe direction to lift the cable and crane load.

Still another object of the invention is to provide a hand-cranked geardrive mechanism connected to produce rotation of the hoist cable drum ofa crane in a manner which will enable a high rate of lifting speed underheavy load conditions and which will further provide an automatic brakeof the mechanism upon reverse rotational drive, the automatic brakingmeans being further effective in proportion to the weight of the load toproduce an increased braking force with increased loads.

The invention in one of its principal aspects provides for a rotatabledrive shaft having a hand-crank on one end. On the other end of thedrive shaft is keyed a worm mounted in operative association with a wormgear connected to the lifting cable winding drum or sheave. The worm andworm gear are of a low ratio design to provide a relatively high liftingrate of speed for the crane mechanism and therefore are essentiallyreversible in drive characteristics. A thrust bearing assembly of theball bearing anti-friction type is associated with the drive shaft andworm in such manner as to absorb the end thrust of the worm underrotation. The provision of the anti-friction bearing assemblyfacilitates the ratation of the gear mechanism in response to rotationof the hand-crank, in a direction to achieve a lifting motion by thecrane, but is also effective in either direction of rotation, since thethrust from the worm is always in the same direction regardless of thedirection of rotations. In order to prevent spontaneous rotation of themechanism in reverse direction in response to a heavy load being loweredby the crane mechanism, this form of the invention provides for anautomatically operable one-way clutch mechanism to be operated inresponse to the reverse direction of rotation during the lowerin motionof the crane to apply a brake upon the rotation of the driving shaftcarrying the worm. Such automatically operable brake mechanism may be sodesigned as to be responsive to the amount of loading on the cranemechanism producing the reverse lowering direction of rotation, so thatthe braking effect increases with and is a function of the load, thusproviding adequate braking effect to prevent spontaneous rotationirrespective of load.

Further objects and advantages of the invention will be apparent withreference to the following specification and drawings, in which Figure 1is an elevational view of a crane mechanism associated as an integralunit with a centrifugal machine shown in part;

Figure 2 is a longitudinal section through the axis of the drive shaftof a worm gear type of crane hoist mechanism embodying the features ofthe invention;

Figure 3 is a plan view of the ratchet collar as used in theautomatically operable one-way clutch associated with the drive andbraking;

arrows on the line 6-5 of Figure 5.

Referring to Figure l of the drawings, in which a crane mechanismunitarily associated with a centrifugal machine is shown for the purposeof illustration, the crane boom I6 is rotatably mounted upon the supportH which is bolted at 42 and I3 to suitable flanges on the body of acentrifugal separating machine M. A locking .mechanism having anoperating hand wheel i6 -may be provided to lock the position of thecrane ID in any desired rotational position such as the position inwhich the crane hook ['6 is over the centrifugal machine l4, or theposition in which the hook I6 is away from the centrifugal ma-- chine M.The lock mechanism and operating handwheel l do not form a part of thisinvention and may be of any form suitable for the purpose.

Enclosed within the crane boom 16 and rotatably mounted at 2B is a cablewinding drum or sheave 2| carrying therewith the worm gear 22.. Thelifting cable 23 is wound around the cable drum 2i and passes over thepulley 24 to be connected at its remote end to the crane lifting hookl6. A drive shaft 25 is journaled within suit-- able bearings (not shownin detail) within the crane boom housing and mounts a worm 25 inoperative association with the worm gear 22. An operating handle 21 isalso provided on one end of the driving shaft 25 (as shown) to enablemarual rotation of the operating shaft 25 and worm 26 to cause a raisingor lowering of the crane cable 23 by winding or unwinding such cableupon the drum 2|.

, 1n the hand-cranked crane mechanism as described for use in connectionwith the lifting of the bowl of a centrifugal separating machine, it isdesirable to have a low gear ratio such as to provide a high liftingrate of speed in order to be able to lift and change separator bowls asquickly as possible. When designing a worm hoisting gear mechanism foruse in hand-cranked crane assemblies, and of a physical size smallenough to be mounted within the crane boom while still obtaining thedesired gear ratio, it is necessary to provide a relatively high pitchfor the worm. The provision of a high pitched worm and worm gearassembly results in a mechanism which is essentially reversible in itsdrive characteristics so that the load on the end of the crane cablewould tend to produce a reverse driving through the worm gear mechanismof the drive shaft and handle once the load had started spontaneously tolower. This invention provides for an improved worm gear drivingarrangement of such type in which the reverse driving of the gearassembly by the load at excessive rotational speeds is substantiallyprevented by the automatic operation of the combined one-way clutch andbrake assembly to be described in the following paragraphs.

The details of one form of combined one-way clutch and brake mechanismin association with a worm gear driving mechanism are shown in Figures 2through 6 of the drawings. Referring to such figures of the drawings,the worm 26 is pinned to the drive shaft 25 by the pin 30. A ratchetcollar 3! is co-axially mounted on One end of the worm 26 (as shown),and is also connected for rotation with the shaft 25 and worm 25 by thepin 36 which passes through the pin bores 32 and 33, as shown inFigure 3of the drawings. Also as shown in Figure 3 of the drawings, the ratchetcollar3l is provided with a plurality of ratchet indentations 34, 35 and36 .having the tapering bottom surfaces approaching the end surface ofthe collar as at 31, 38 and 39, 'respectively. Such ratchet indentationsare conventional in having steep end side walls 40, 4| and 42,respectively, opposite to the tapering port-ions 31-55, respectively.

Again, referring to Figure 2 of the drawings, it will be seen that aratchet pawl collar 45 is coaxially mounted around the main drivingshaft 25 freely rotatable in a manner to be normally not connected forrotation with the shaft 25, as shown. The main driving shaft 25 may bejournaled in non-rotatable member 46 fastened by bolts 41 and 48 to thecrane boom housing l6 partially shown in Figure 2. The ratchet pawlcollar 45 is provided with an end wall surface 49 in frictionalengagement with the end wall surface 56 of a non-rotatable member 46fastened to the crane housing iii, as previously described. Theanti-friction ball hearing assembly 5! is interposed between the thrustend of the worm 25 and the internal wall surface 52 of the ratchet pawlcollar 45 which, as previously mentioned, is freely rotatable upon theshaft 25. It will be seen that the anti-friction ball bearing assembly5! functions as an anti-friction thrust bearing, and that the pawlcollar es and member 46 at their respective surfaces 49 and 50 cooperateto form what may be termed a friction thrust bearing or brake.

Referring to Figures 2, 5 and 6 of the drawings, it will be seen thatthe ratchet pawl collar 45 is provided with a plurality of pawlreceiving pockets 55, 56 and 51 within which the ratchet pawls, such asthe one shown at 58; are journaled against the compression of pawlsprings such as shown at 59. It will be noted that each of the ratchetpawls such as 53 are urged by their respective compression springs suchas 59 into engagement with the ratchet indentations 34- 36 of theratchet collar 3|. Such an assembly of ratchet and ratchet pawl collarsis representative of one form of automatically operable oneway clutchwhich may be used in the drive system of this invention.

A clockwise rotation of the shaft 25 by manual operation of the handle23' or otherwise to produce a lifting motion of the cable drum 24 willalso cause clockwise rotation of the worm 26 and the ratchet collar 6!.The ratchet indentations 34-36 are shaped to permit a ratchet releaseaction by each of the spring-pressed pawls and cause the ratchet collar3! to rotate without rotating the ratchet pawl collar 95 duringclockwise rotation of the ratchet collar. Thus, the end thrust from theworm 25 for clockwise rotation of the shaft 25 is absorbed by theantifriction ball bearing assembly 5i between the thrust end of therotating worm 26 and the nonrotated pawl collar 45 freely rotatable onthe shaft 25 but held against rotation by the worm end thrust forcingthe frictional surfaces 49 and 59 together. In such manner the liftingforce is applied to the cable drum 2! in a relatively frictionless modeaffording easy operation during clockwise rotation of the drive shaft25.

Upon reverse or counter-clockwise direction of rotation of the shaft 25,in response to a reverse rotation of the handle 27 assisted by (butpreferably not caused by) the gear mechanism from the worm gear 22through the worm 26 due to heavy loading on the crane and the high pitchof the worm, each of the ratchet pawls will engage one of the respectivesteep end wall surfaces 49, 4| or 42 of the ratchet indentations S t-66to cause a rotation of the ratchet pawl collar 45 with the ratchetcollar SI and the worm 26 pinned to shaft 25. The counter-clockwiserotation of the ratchet pawl collar 45 is resisted by the frictionalcontact between its end wall surface 49 and the end wall surface 50 ofthe non-rotatable journal member 66 as produced by the end thrust of theworm 26. Thus the frictional brake surfaces 49 and 59 are preferably ofsuch size and arrangement as to be effective to provide a sufficientfrictional brake against any spontaneous rotation of the shaft 25 as aresult of a load on the crane.

It will be noted that the thrust of the worm gear 26 through the ballbearing assembly 5| against the pawl collar 65 will increase thefrictional contact between the surfaces 49 and 59 as a function of theincrease of such thrust or loading of the crane. Thus, the brakingeffect against counter-clockwise rotation of the driving shaft 25 in theworm gear mechanism of this invention is automatically obtained inresponse to such counter-clockwise rotation and is variable in effect toincrease the braking force with increases in the amount of loading onthe gear mechanism causing the reverse rotation. Such braking effect isobtained through the medium of the automatically operable one-way clutchor ratchet mechanism in association with an antifriction bearingassembly in such relation that clockwise rotation of the shaft 25 isenabled under relatively frictionless conditions, the braking surfacesbeing rendered ineffective during such clockwise rotation.

The braking effort may be varied by changing the character of thesurfaces 49 and 50, and also by varying the radius from the axis of theshaft 25 at which the surfaces 49 and 50 contact with respect to theradii of the teeth on the worm 26. By such variation the braking forcecan be adjusted so as to be preferably at least slightly greater thanthe rotational force due to a load on the crane, thus preventingspontaneous rotation from such a load. -With such adjustment only aresultant or differential force need then be applied to the handle 2? tolower the load on the crane.

It should be pointed out that the gear driving mechanism and automaticbrake arrangements of this invention are not to be limited to a specificadaptation in crane mechanisms, either in association with or withoutcentrifugal separating machines, since the reversible gear drive havingautomatic braking means may find useful application in various othermachines and devices.

Modifications will be obvious to those skilled in the art and I do nottherefore wish to be limited except by the scope of the claim.

What is claimed is:

Crane hoist mechanism, comprising a rotatable shaft, a worm secured tosaid shaft, a worm gear operatively associated with said worm, said wormand said Worm gear having enmeshed teeth of a sufficiently high pitch tocause said Worm and Worm gear to be essentially reversible in drivecharacteristics, means for connecting a liftinglowering load to saidworm gear to cause a unidirectional torque thereon, a ratchet collarcoaxially and fixedly mounted on said shaft at the thrust end of saidworm and rotatable therewith, a second ratchet collar coaxially mountedon said shaft next, to said first-mentioned collar with saidfirst-mentioned collar nearest said worm gear, said second-mentionedcollar being rotatable relative to said shaft, an antifriction thrustbearing operatively positioned between said first-mentioned andsecond-mentioned collars, ratchet-means associated with said collars andadapted to automatically engage said collars when said worm is rotatedin a lowering direction and to disengage said collars when said Worm isrotated in a lifting direction, a bearing for said shaft having saidcollars and said worm on the same side thereof, a brake face on saidbearing adjacent said second-mentioned collar, a juxtaposed brake faceon said second-mentioned collar, said bearing brake face and said collarbrake face being held in frictional contact by the thrust on said wormdue to said unidirectional torque on said worm gear, and means forrotating said shaft.

HAROLD C. FITZSIMMONS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,257,576 Boehock Feb. 26, 19181,287,966 Gormley Dec. 17, 1918 1,756,459 Gormley Apr. 29, 19301,892,940 Erdahl Jan. 3, 1933 2,408,179 Schuetz Sept. 24, 1946 FOREIGNPATENTS Number Country Date 113,136 Germany Apr. 15, 1899 2,684 Great.Britain A. D. 1906 195,331 Great Britain Mar. 29, 1923

